Induction furnace



Patented Sept. 22, 1931 UNITED STATES PATENT OFFICE I THOMAS H. LONG, OF IRWIN, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA INDUGIION FURNACE Application fled September 20, 1930. Serial No. 483,242.

My invention relates to electric furnaces and particularly to induction furnaces.

An object of my invention is to provide a relatively simple form of energizing coil for an induction furnace which shall have minimum electrical losses therein. 7

Another object of my invention is to provide.an ener zing coil'embodying a plurality of laminated parallel-connected con 10 ductors to reduce the energy loss therein, and

through an induction furnace embodying my invention, shown in part only;

Fig. 2 is a view, in developed front elevation, of a portion of a heat shield constituting a part of the device embodying my lnventlon.

Fig. 3 is a fragmentary sectional view of a modified form of a portion of the device embodying my invention. 7

. Fig. 4 is a schematic diagram illustrating the connections between adjacent turns or groups of turns of my multi-layer coil.

It is obvious that it is highly desirable, if

not actually necessary, to maintain the temperature of the energizing coil of an induction furnace at as low .a value as may be possible, in order to prolong the life of the coil and that ofthe insulating material, as well as to maintain the electric-current losses therein at a reasonably low value.

To this end, I laminate the conductor and shield it by a fluid-traversed heat screen from the material being heated.

A sheet-metal casing 11 is shown in Fig. 1 of the drawings that may be of any suitable or desired construction and may be made of a metal which is non-magnetic, in order to reduce the eddy-current losses therein. A crucible 12, of refractory material, is located in the casing that may also be made of any suitable or desired material usually employed for such purposes and of any suitable shape. A quantity of electric and heat-insulating granular material 13 is located within the casing 11 to enclose and suport the crucible 12, all in a manner known in the art.

An energizing coil,including a plurality of turns of a plural-element conductor 14, is employed, only one side of one turn being s.hown,it being understood that the other turns are like that shown. The conductor 14 includes a plurality, of relatively thin strips 16, 17 and 18 of copper, which are separated from each other and "fromfa tubular conductor 21 by relativel electric-insulating .materia 19, the conductor 21 being traversed by a cooling fluid, such as water or air. The tubular conductor 21 is ti-element conductor 14, as is shown in Fig. 1 of the drawings, and I may employ a tubular member 22 of solid electric-insulating material, such as mica, between the strip 16 and the crucible 12.

I provide also a fluid-traversed heat screen 23 between crucible 12, which is, of course, to contain the materialv being heat treated, and the coil, and locate it between the outer wall of crucible 12 and the member 22. The

heat shield 23 includes a flattened tubular member which may be built up in any suitable or desired'manner, as bybrazing suitably formed sheets of copper to constitute a structure of serpentine shape, substantially as shown in Fig. 2 of the drawings, it being understood that the number of convolutions is such as to extend around the crucible 12. An inlet end 24 is provided to permit of connecting a suitable. hose thereto which should preferably be made of electric-insulating material to permit the cooling fluid to enter the heat shield at this point and to discharge it at the exit end 26, closely adjacent to the inlet end 24. It may be desirable to circulate 4 the water through the thermal shigld in a plurality of parallel-connected at s. p It is highly desirable to insure that all of the elements 16, 17 18 and 21 which are to be connected in electric-conducting relation thin layers of preferably located on the outside of the mulshall be subjected to a uniform electric loading, as regards the flux generated thereby,

and I have illustrated, in Fig. 4 of the drawings, one means of accomplishing this. The respective elements of the conductor are illus-' trated schematically only, and, after one turn or group of turns of the coil'has been completed, the end of element 16 is connected to the second conductor element, asindicated,

in aradially outward direction, while ele-' ment 17- is connected to the third element of the second turn, and element 18 is connected 1 tothe fourth element ofthe second'turn,

while element 21 is connected to the innermost element of the second turn. This 'method of connection is repeated for all of the turns and will result in a substantially uniform electric loading of all the elements in all of the turns. r 1

Referring more particularly to Fig. 3 of the dr'awings,.I have there illustrated one turn of an-energizing coil embodying eight parallel-connected conductor element'sand it maybe noted that the innermost member 21 will be operative,- notjonly to-dissinate heat from those conductor elements inside thereof,

. but also from those c'onductorelements outside thereof. I have-illustrated the annulus 22 of mica, but have not illustrated the crucible or heat shield, as all of the otherparts are the same as shown in Fig. 1 of the drawings. As was hereinbefore set forth in connection with Fig. 1, only one turn of a helical plural-turn energizing coil has been illustrated, and it is to be understood that the coil extends downwardly to near the bottom of the crucible.

. The device embodying my invention thus provides a laminated conductor in which the radial thickness of the conductor elements is made such that the eddy-current losses there-.

in are relatively small and whereby means for maintaining the temperature of the conductor at a relatively low value by the use of the fluid cooling-current-traversed element 21. v

As acoil of this type may be used, not only for the melting of metals but also for the heating of solid blocksof metal. the temperature within the coil may be relatively high and, in order to prevent over heating of the coil, I provide the heat screen embodying the fluid-traversed flattened tubular member, hereinbefore described.

While I have illustrated and described a plural layer coil in which the respective layers are connected in parallel-circuit relation, they may be connected in series-circuit relation.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art orare set forth in the appended claims.

I claim as my invention:

1. In an electric inductive heating device, a plural-turn energizing coil embodying a -vided shield between the coil and material to be heated to reduce flow of heat from heated material to the coil, and a fluid-traversed cooling means substantially; coextensive with said conductorand operatively engaging the same.

3.- In an electric inductive heating device, an energizing coil having a plurality of turns of a radially-laminated conductor, said con- 1 ductor including an, outermost hollow fluidand-current-traversed lamination and a fluidcooled-subdivided shield between the coil and material to be heated.

4. In an electric inductive heating device, an energlzing coil for inductively heatin' material and embodying a radially-laminate conductor, a fluid-cooled subdivided shield located between the coil and material being heated, a portion of said conductor constituting a fluid-coolin means substantially coextensive, and 010 therewith to carry away any heat generated therein by the passage of an electric current therethrough.

5. In an electric inductive heating device,

an energizing coil embodying a conductor subdivided radially so that the current density. in the respective portions is substany operatively associated tially uniform, and a cooling means located between the coil and a material being heated.

6. In an electric inductive heating device, an energizing coil having a plurality of layers of a laminated conductor, an intermediate lamination being hollow and fluidtraversed, and a laminated fluid-cooled thermal screen between the coil and material being heated to reduce heat flow from the heated material to the coil.

In testimony whereof, I have hereunto subscribed my name this 12th day of September,

THOMAS H. LONG. 

